It is a gross over-simplification - but I've had a lot of managers, and not once have I seen one bust their ass for a year, and then take six months to gather feedback and peer support on their work, in order to get the rapport necessary to do the job they were hired to do.

I mean, they do this sort of thing, in order to show that they are superstar, and should get 2x the headcount they currently have, but they don't actually need to spend a year and a half convincing people with results, in order to be allowed to direct their existing headcount as they see fit.

A senior IC, on the other hand, needs to personally prove themselves at every workplace, before they are allowed to act in the role of a senior. You're expected to deliver the results of a manager, without the corresponding power. You're expected to exercise soft power, and you're expected to acquire this soft power on your own.

It is an incredibly inefficient way of getting stuff done, if you ever switch jobs.